1. Field of the Invention
The present invention relates to a method for managing a conference call in a telephone network, in particular, but not exclusively, in a mobile telephone network. The present invention further relates to a computer program, a conference call server and a terminal for implementing the method.
2. Description of the Related Art
Current telephone networks, either fixed or mobile, are adapted to provide their users with a plurality of telephone services, such as call screening, call answering service, or the like. Current telephone networks are also adapted to provide their users with a conference call service. Such a conference call service allows to set up a telephone call among a plurality of users, each user being connected to the telephone network through a respective terminal (either fixed or mobile).
U.S. Pat. No. 6,839,417 B2 discloses a method and apparatus to allow individuals to initiate, join, manage, and participant in a conference call. Each participant has a station, consisting of at least a telephone, a processor, a display written by the processor, and controls provide the participant with input to the processor. The telephone and processor are in communication with other participant stations via a conference server. The conference server is also responsible for providing, for each participant, a combination of the other participants' voices. When a speaker is designated, this combination ensures that the speakers voice is able to dominate the combination for each of the other participants. Even so, the other participants are still audible within the combination, and the other participants are preferably audible to the speaker.
A known conference call service includes an activation phase, which can be performed in different ways. For instance, a user (which will be termed in the following description “master user”) who wishes to activate a conference call may call each user to be connected to the conference call (which will be termed in the following description “member user”). Alternatively, the master user may request the activation of a conference call, which will be performed in a centralized way, as it will be shown herein after.
According to this known conference call service, at the end of the activation phase, master user and member users are bi-directionally linked the one to the others. In other words, during the conference call, the terminal of each user participating to the conference call continuously transmits and receives signals through the common voice channel.
More particularly, during the conference call, the terminal of each user receives signals transmitted by the terminals of all the other users participating to the conference call. A signal transmitted by a listening user terminal only comprises environment noise (as it will be discussed herein after), while a signal transmitted by a speaker user terminal comprises both speech and environment noise.
The Applicant has perceived that this known conference call service has some drawbacks.
First of all, as each user (either master or member) who is participating to the conference call is bi-directionally linked to all the other users, he can start speaking whenever he wants. This could disadvantageously lead to a situation wherein more than one user speak at the same time, so that their speeches overlap and become hardly intelligible by the listening users.
Moreover, if a number of users is participating to a conference call by means of a single terminal (possibly by using the hands-free function of the single terminal), any comments that such users exchange with each other are transmitted to all the other listening users, thus overlapping to the speech of the speaking user, which could become hardly intelligible by the listening users.
Moreover, as each user participating to a conference call is located in a respective location (such as in his car, in his office or in his factory), during the conference call, as already mentioned, the terminal of each user continuously transmits an environment noise to the other users. Therefore, each listening user continuously receives an overlap of the speech transmitted by the speaker user and of the environment noises transmitted by the speaker user and by other listening users. If a user is located in a highly noisy environment, or if more than one user are located in a noisy environment, the overall environment noise level may be comparable to the speech level, so that the speech of the speaking user become hardly intelligible by the listening user.
This problem is particularly significant in case of conference call services in a mobile telephone network. Indeed, it is likely that one or more users participating to the conference call are located in a noisy location, such as on a street or on a car. Besides, in mobile telephone networks environment noise affects speech more severely than in fixed telephone networks, due to the fact that in mobile telephone networks signal coding (such as AMR coding, which is typically used in GSM telephone networks) uses less bits, thus implying a lower signal quality (speech intelligibility, speaker recognizability, or the like).